1. Field of the Invention
The invention relates to hull design and construction and in particular to the creation of original hull designs and the construction based on them. More particularly, the invention relates to a method for systemizing the creation of an original lines drawing in a way that permits the hull-defining frames to be drawn from a single template and the physical frames to be constructed from a single template, so as to shorten the time required at both the design and construction stages for any type of frame-based watercraft that is not a reproduction or facsimile of an earlier vessel. Furthermore, the use of the single template to define the curve along the entire length of the hull results in less turbulent, and hence more rapid, passage of the resulting boat through the water.
2. Description of the Prior Art
An original hull has a shape not previously in existence. It is based on drawings created specifically for the vessel of which it is a part, which is therefore an original vessel. Designing and constructing an original vessel are time- and labor-intensive undertakings; hence, the high cost of owning a original vessel, and the relatively small number of boatyards specializing in original boat design and construction.
Although mention of unique vessels often conjures up wooden sailing craft, originally vessels currently being built are by no means limited to that type of watercraft or to that material. At any event, decisions regarding type and material are usually, though not always, made before the designer and the builder of the craft have been hired. Typically, the designer will have as givens, in addition to the type and material, the overall length and beam (width) of the vessel. Starting with those parameters, and usually the load-bearing capacity of the original vessel to be created, the designer relies on his experience, education, and instinct (his design sense) to produce the drawing that will serve as the vessel""s blueprint. This is the xe2x80x9clines drawing,xe2x80x9d the lines including the sheer line (defining the top of the hull, where the hull joins the deck), and the hull""s bottom line (which incorporates the keel line, where the hull joins the keel, if there is to be a keel), and the water line. They also include a number of the hull""s longitudinal contours as well as the (related) shape of the hull""s transverse cross-sections at many locations (xe2x80x9cstationsxe2x80x9d) along the length of the vessel. These cross-sectional shapes define the shapes of the frames that will form the skeleton of the vessel. The more complex the hull shape, the more such cross-sections are necessary to define the design for later construction. The lines drawing, in combination with a table of offsets numerically specifying the locations of particular points within the hull, defines the new hull. It is typically drawn to a scale of 1:24 (half-inch to the foot) and, when complete, expanded to a full scale (xe2x80x9cloftedxe2x80x9d) version. In the case of traditional wooden-boat construction, this lofted version is painted on the floor of the boat builder""s shop.
Among boat builders and designers, important term and practice is xe2x80x9cfairing,xe2x80x9d or xe2x80x9cmaking fairxe2x80x9d the lines of a design. Also, the lines of an existing boat can be described as xe2x80x9cfairxe2x80x9d or xe2x80x9cnot fair.xe2x80x9d This refers to the smoothness of the lines, and also to their relative monotonicity. A sheer line is fair if it makes a continuous sweep from one end of the vessel to the other, typically sinking as it progresses from the stem to midships, then rising again as it progresses the rest of the way to the stern. It is not fair, however, if during this sweep it falls and rises repeatedly and/or for no logical reason.
One of the reasons for the traditional of transferring the scale lines drawing to a full-size version is to check for the fairness of the lines. Irregularities not visible on a small scale may show up in the full-scale drawing.
The physical hull is built up starting with construction of its skeleton, the series of frames oriented perpendicularly to, and deployed along, the hull""s longitudinal axis. The shape of each frame is defined by the shape-given the hull at that station during the design stage. Working from the full-scale drawing, the builder constructs each of the full-scale frames. When the building material is wood, one may make molded frames by bending a single piece of wood bent to the proper shape using a mold, which in turn was made using the full-scale drawing. Alternatively, one may make sawed frames out of a single large piece of wood or, more commonly, several pieces of wood affixed to one another and then the composite sawed to the proper shape. For the latter approach, a full scale drawing of the individual frame may be made on plywood or the like to serve as an outline for the sawing. Once constructed, each frame is placed at the proper station in the hull taking shape overhead as the construction progresses.
The number of frames needed depends on the requirements of the vessel; typically it is several score. Although there is a relationship between the frames determined by the architect""s drawing, there is no simple way of determining the shape of one frame from the shape of another frame, even a neighboring one. The drawing and construction of frames contributes significantly to the total time, and hence expense, of building a newly designed vessel. The need to derive and construct each frame as a separate undertaking is one of the factors that makes the construction phase so lengthy.
For more than 100 years, extending down to the present time, the method just described is the way that original hulls have been created. For all that time, much of the cost of producing hulls has come from this frame by frame by frame approach. Although a hull, once designed and constructed, can form the mold for repetitive and relatively inexpensive copying, originality of design is a good that has always driven the market for new boats, especially where sailing craft and other sporting boats are concerned. It is, however, a good that is difficult to acquire because of the high cost of producing unique boats.
Therefore, what is needed is a method to produce original hulls in a manner requiring less time than the method now in use. What is further needed is a method that is more efficient both at the design stage and at the construction stage of original hulls. What is yet further needed is such a method that can be implemented in the boat-building craft as it is presently constituted.
The object of the invention is to introduce an approach to the creation of hull designs that allows the designs to be more efficiently created. It is a further object of the invention that the designs thus created permit the hull-construction based on them to be carried out with less effort and time than is the case with current hull designs. Finally, it is an object of the invention that the efficiencies made available by the new approach be immediately adaptable by existing naval architects and boat shops that produce either wooden or non-wooden vessels.
The present invention meets its objectives by a reversal of the traditional approach to hull design. Instead of first creating the lines drawing and then determining from that drawing the shape of the individual frames, the design approach of the present invention involves generating the lines drawing from the shape of a single curve, a Single Frame Curve (SFC), which can also be referred to as a Master Curve. Then, during the physical construction of the hull, the Single Frame Curve is used to generate all of the frames for all of the stations, each of the individual frame shapes being found along a segment of the Master Frame. Because of the single-frame approach made possible by the present invention, only one frame curve need be designed, only one frame mold need be constructed, andxe2x80x94because all frames are just different segments of the same curve (that of the Single Frame Curve)xe2x80x94there is less chance of error in the lofting of the frames. The method begins to be implemented at the hull-drawing stage, where the Single Frame Curve template is created, and later carries through to the actual construction of the hull.
Although the details of the hull are generated from the Single Frame Curve, the latter is created in detail only after the general lines of the desired hull are limned. With no constraints other than beam and length specs, the architect/designer produces a lines drawing limited to the profile (side-view) and deck (top-view), using the keel line (or other hull-bottom-characterizing line, such as the rabbet line). Then a horizontal line is added to the profile to represent the initial Design Water Line (DWL). At this point, very little has been defined regarding the details of the hull. Not having provided the hull shape at any station, let alone a distribution of stations, it is not possible to say any about the shape of the water line, that is the outline of the hull""s intersection with a horizontal plane passed through it at the DWL.
Next, a number of vertical lines are added to the diagram, defining the respective positions of an equal number of stations, typically ten. Generally, these will be equally distributed between the fore and aft intersections of the DWL with the bottom of the hull, as is traditionally done in the first stages of hull design. The deviation from the traditional approach begins with the following step, when the designer draws a tentative curve to represent the shape of a frame at a station near or at the widest portion of the hull. After a series of iterations, to be described below, this tentative curve is xe2x80x9cmorphedxe2x80x9d into the Single Frame Curve that is at the heart of the inventive method. It is important to realize that this method neither deprives designer of originality, nor adds to his or her artistic and engineering sense, but provides a way in which the abilities of the designer are more likely to result in a new boat being built. It does this by allowing the designer and boat builder to practice their respective crafts jointly and less expensively and hence to find more outlets for them. An analogy may be made with the sculptor who, after working for years with hammer and chisel, is provided with a power tool that when properly handled can remove stone as precisely as the hammer and chisel, though at a much faster rate. Thus, the new tool and method are a contribution to the sculpture""s practice, even though the engineer who created them is not able to tell the sculptor how to produce an artistically pleasing sculpture with them. The final product will still depend on the skills of the sculptor.
In drawing the tentative single-frame template (xe2x80x9ctest framexe2x80x9d), the only constraints facing the designer, once the station has been chosen, are the are the respective distances that the top and bottom of the frame are offset from the vessel""s centerline. The designer then uses his or her instinct to shape the test frame. Aiding in this is the DWL, since in drawing the test frame, the offset of the point on that test frame which intersects what waterline is apparent. That is, the shape of this test frame defines how far the water line is outboard from the centerline at the station chosen. At any event, the test frame provides a single data point regarding the shape of the water line as viewed from above or below. With that point defined, the designer draws in the rest of the waterline, again based on his or her skills and vision for the boat. This defines the hull""s shape at the waterline, a shape that may be changed as the process continues.
After the test template is drawn to comply with the shape that the designer wishes to give to a frame at a midships station, it is extended at the top (above the deck height) and below (below the keel line). The goal is ultimately to have a curve, longer that any particular frame, having a shape such that each frame in the hull will be able to be matched up with one or another portions of the curve. That will be the nature of the SFC that emerges from the first part of this process. It is because the hull at midships is usually most defining of the type of vessel being designed that the midships station is the one normally chosen as the starting point, so that the frame there will comply with the central portion of the SFC.
Having begun with the test frame and resulting test SFC, the designer using this method then works back and forth between the shape of the SFC and the shape of the hull until a particular goal is reached. That goal is to have (1) an SFC that satisfies the requirement that every frame on the hull can be fit at some portion along the SFC curve and (2) the hull design that results is fair and comports with the designer""s objectives. The iteration stagexe2x80x94to be explained in some detail belowxe2x80x94will typically go through several cycles before all the proper elements of the hull design come into balance. When it is completed, the SFC is used to draw all of the frames that are desired in the small scale drawing. The scale drawing is then lofted (scaled up) in the boat shop, typically being laid on the floor. Concurrently, a Master mold is produced from the SFC, a single mold that can be used for the construction of every one of the physical frames that are to become the backbone of the boat.
Because the trial-and-error portion of the method is executed with paper and pencil on a small-scale drawing at the outset, the overall process of preparing full drawings and of constructing the vessel is completed with a significant savings of time and materials in comparison with the present means of designing, lofting and constructing boats.
The details of the iterative stage are as follows. For definitiveness, it is described in terms of traditional materials, including paper. It is understood, however, that the most widespread application of the method in the future will be done with the use of computers. The translation of the steps set out below from traditional materials to software counterparts of these materials will be obvious to those having professional kills in modern boat building, a field that is turning ever more to the use of computers for design and construction. It is also to be understood that where some definite traditional material, such as tracing paper, is mentioned there is no intention of limiting the method to that specific material. The use of any materials or technology enabling one to achieve the steps called for will be within the ambit of the present invention.
Using traditional materials, the designer transfers the tentative SFC to tracing paper, and lays the tracing paper onto one of the stations near the stem or stern of the hull as depicted in the initial lines drawing. This is because it is generally in those stations that the frames will differ the most from those amidships. (Depending on the particular type of vessel, this may not be true. To continue to provide definitiveness to the discussion, a particular vessel is envisioned, namely a sailing craft. However, the method of the present invention can be applied across the entire range of boats, from small sailboats and motor launches through large oil tankers and indeed submarines. It has value wherever the boat in question is to be of a new design.)
With the tentative SFC overlaying the station near the stem or stern, the designer seeks to find a portion of the tentative SFC that will have the shape and extent of a frame that meets the conditions required at that station. The conditions are that the bottom of the frame coincide with the keel line""s position at that station, that the top of the frame coincide with the sheer line at that station and that the frame intersect the waterline at the point dictated by the waterline curve drawn earlier in the process. In other words, the frame must extend between the keel line and the sheer line and intersect the DWL (water line); the latter condition is meant if the frame, at the height of the DWL, is the same distance outboard from the center line as the DWL itself. In practice, the test of these conditions is carried out by referring to both the side view and the top view in the lines drawing.
In summary, one must be able to position the SFC so that a portion of it extends from the proper point on the keel line to the proper point on the sheer line and has the proper offset at the height of the waterline. If this is not possible, something has to modified. It can be the shape of the waterline. It may be the shape of the SFC. If the latter""s shape is modified in its central region, which tracked the originally selected midships frame, then the latter itself must be modified. This is unusual, however, given that some thought went into the first-order drawings. It is more common to have little or no modification necessary or that, if a modification in the SFC is indicated, it can be done outside the central region of the curve.
When, after a few iterations, the SFC can be made to fit both the initially chosen frame (or a slightly modified form of it) and provide the shape of an acceptable frame at one or two points at the extreme ends of the hull, the operational SFC has been attained. It is important to note that the freedom of design is primarily exercised when drawing the initial lines of the vessel, including the hull shape at the waterline and the tentative SFC, at the outset. The other frames drawn at the design stage are to a large extent pre-determined by the choices made at that point.
Once the operational SFC has been attained, a piece of cardboard or some other stiff material is cut out so that one edge corresponds to the SFC shape. This forms the template that will be used for drawing in the frames at all of the other stations. Before drawing these frames, however, the designer places a Reference Mark near the midpoint of the template. (The exact position is not critical.)
The frames are then drawn using the side-view perspective of the lines drawing. At each station, a portion of the template is found that will permit a frame satisfying the conditions at that station, as was done at the stage where the tentative SFC was tested at the stem and stern of the hull. As one progresses from one station to the adjacent one, one attempts to find the desired frame shape as close as possible on the template to where the previous frame shape was found (this normally occurs automatically, because of the absence of equivalent shapes at more than one place on the template). At each station, in addition to drawing the frame in, the designer makes a mark (a Reference Point) at the point where the Reference Mark on the template is located. This is typically done at ten different stations, distributed equally from the aft frame to the front frame. However, there will generally be considerably more frames actually constructed during the physical creation of the boat.
After the frame curve at each of the pre-selected stations has been drawn, the designer draws a smooth curve, the Reference Line, that passes through all of the Reference Points. The Reference Line should have a shape corresponding to the type of boat being designed and, within that type, with the form for the boat envisioned by the designer. For example, the hull of a sailing yacht will have a relatively narrow bow (stem) and wider stern. For such a case, Reference Line should arc upward toward the deck line as it approaches the stern, and, conversely, become flatter and closer to the keel line as it approaches the bow. If the Reference Line does not look appropriate for the type of boat being designed or if its slope is varies rapidly as one progresses along the length of the vessel, the designer needs to return to an earlier stage in the process and reexamine his or her choices for basic lines. In particular, the designer may reshape the SFC or reposition the template at any of the stations (for drawing the frames) as many times as is necessary to effect the desired result. It is anticipated that the need to re-iterate once the Reference Line stage has been reached will not generally occur with experienced designers, at least after their first few efforts with the SFC method.
If the Reference Line is fair, then one advances to the next stage, which involves adding in the additional frames that needed to guide the ultimate construction. This is easily done using the Reference Line. The template is placed at each station where one wishes to add a frame curve, taking care to position the template so that the Reference Mark on it coincides with the Reference Line""s intersection with that station. With the Reference Mark so placed, it is only necessary to rotate the template so that it makes contact with the sheer line and keel lines, respectively. The waterline should take care of itself, given the preparatory steps preceding this stage.
Once the design of the hull""s shape has been completed, the scale diagram is lofted to full scale in the boat shop. However, unlike the traditional approach, it is not going to be necessary for the boat builder to work so intensively with the drawing. This is because of the known relationship between the different frames. One approach to implementing this knowledge is to construct a single mold reflecting the SFC developed at the design stage. Then every single frame can be constructed using this mold, though different frames in general will be build using different portions of the mold.
The following is a summary of the method of this invention, presented in recipe form. It is to be understood that the invention is not limited to the specific details given below, details such as the prescription that a line be dashed that are provided just to add definitiveness to the instructions. It is also understood that most of the detailed steps set out in this xe2x80x9crecipexe2x80x9d are already well understood by professional boat designers and are only included here for completeness. In particular, the concept of working iteratively in completing a drawing is well understood.
1. Choose and lay out the proposed vessel""s sheer line and bottom line commensurate with the vessel""s beam and length requirements on (a) a half-breadth top view, defined by the sheer line and the centerline, and (b) a profile view (xe2x80x9cside viewxe2x80x9d) defined by the bottom line, which will include the keel line, and the sheer line. To the half-breadth top view add the half-breadth keel line as a dashed (invisible) line. On the side view, show the desired height of the waterline as a dashed horizontal line. The two views are to be given their traditional locations, the top view being placed directly above, and aligned with, the side view. Also, as is the traditional practice, the half-breadth top view depicts the port side of the vessel and the profile view the starboard side. This has only formal significance, given the vessels"" bilateral symmetry. (It is also traditional in the lines drawing to include a half-width longitudinal view depicting the frames at a number of stations. It is composite since in the same planar drawing the port-side half of the frames as viewed from the stem are shown along with the starboard half of the frames as viewed from the stern. In this recipe, this longitudinal view is not used. Instead, as a short-cut, the half-frames will be depicted on the side view, each to be shown perpendicular to the vertical line representing it respective station, all as to be disclosed below.)
2. Add to the drawing ten vertical lines depicting ten stations, the forwardmost and aftmost stations coinciding, respectively, with the forward and rear intersections of the DWL with the hull""s bottom line. These vertical lines will pass through both the top view and the side view. The resulting station closest to midships will be designated the xe2x80x9cmidships station,xe2x80x9d even though it is not exactly midships.
3. Where the midships station appears on the side view, draw in a midships frame (actually a half-frame), comporting with your view of how it should be shaped, having as constraints the half-beam and the half-keel width at that point. In showing this midships frame on the side view, present the transverse view in the plane of the paper. The upper end of the half-frame will be displaced to the right of the midships"" station by a distance equal to the half-width of the vessel at that station and the lower end of the half-frame will be displaced to the right of the station by a distance equal to the half-width of the keel at that station.
4. From the midships half-frame just drawn, determine from the horizontal representation of the D.W.L. the point on the frame that will intersect the waterline. Make a mark on the top view indicating that point (which would be an xe2x80x9cinvisible pointxe2x80x9d on the drawing, being obscured by the deck or by the bulk of the hull itself). This is the first point on the two-dimensional shape outlining the vessel""s intersection with the plane of the water.
5. Based on the type of vessel being designed and your own designer""s instincts, draw in the rest of the two-dimensional shape outlining the vessel""s intersection with the plane of the water, taking care that it pass through the point marked in step 4. Although the details of the waterline are left to the professional knowledge and instincts of the boat designer, its exact shape may be altered at a later stage in the process as a result of the feedback that the present method provides to the designer.
6. Laying a piece of tracing paper over the midships frame, trace that frame, and then extend it at the top and the bottom, respectively. This extended curve will be the tentative Single Frame Curve, which, either as it stands or after some modification, is to be the operational Single Frame Curve (SFC) that will govern the design and construction of all of the frames of the vessel to be built by this method.
7. Using the top view for offset information (e.g., how far outboard from the centerline the waterline intersects the hull at that point), place the tentative SFC on the side view at one of the stations near the stem, and try to find a portion of that tentative SFC that will xe2x80x9cfitxe2x80x9d the half-frame at that station. A xe2x80x9cfitxe2x80x9d is achieved when a portion of the SFC is found that extends from the sheer line to the bottom line and has the same offset from the center at the waterline as the waterline itself does.
8. If no portion of the tentative SFC satisfies the conditions to represent a half-frame at the station chosen in the previous step, introduce the smallest modification in either the tentative SFC or the waterline that allows a fit to be made. If you made the modification to the tentative SFC in its central region (an unlikely circumstance) bring the modified curve back to the midships station to make sure that it still fits the midships frame. If it does not, the midships frame may be modified.
9. Do the same thing with one of the stations close to the stern of the vessel. Note that the tracing paper will have to be flipped over to do this, given the traditional depiction being used, where the port half of the frames are shown for the fore-body, and the starboard side of the frames for the aft-body.)
10. Once the tentative SFC, adjusted or not, works for the several test stations, it has attained the status of operational SFC. At this point cut a piece of cardboard so that one edge of the cardboard is in the shape of this SFC; the cardboard will serve as the SFC template for drawing half-frames for the fore-body and aft-body.
11. Place a Reference Mark at approximately the center of the SFC template, making sure to mark it on both sides. The exact location of the Reference Mark is not important, as long as it is somewhere in the central area of the SFC.
12. Using the SFC template, draw in frames corresponding to a few of the stations defined by the vertical lines introduced earlier, using the convention in which all of the half-frames seem to emanate from near the midships station. That is, the offsets of all of the half-frames drawn in are shown with respect to the midships station. The offsets in question are for the half-beam, the half-keel (for those half-frames that connect with the keel) and the waterline. As each half-frame is so drawn, note and mark the height with respect to the bottom or sheer line at that station where the Reference Mark falls. Using that information about the Reference Mark associated with each station where the half-frame is drawn, place that a mark on the side view at the respective station.
13. Using the Reference Points placed as described above, draw a smooth line that passing through those marks. This is the Reference Line, and it should have a smooth sweep to it, and not be significantly non-monotonic, i.e., not go up and down repeatedly as it moves from the front of the hull to the back. Another way of saying this is that it should be fair. If it is not, you must re-examine some of the choices you made along with way, with respect to the ship""s lines.
14. If the Reference Line is fair, the frames can be quickly drawn in at the rest of the stations defined earlier. This can be done either using the central-body transverse view or by going directly to station of interest. First the latter approach will be spelled out. Note where the Reference Line intersects the station of interest, and draw a horizontal line through that point. Place the SFC template so that the Reference Mark lies on that horizontal line. Then pivot the SFC template about Reference Mark (which remains fixed in position on the drawing), so that a portion of it bridges the distance between the sheer line and the bottom line of the hull at that station. (The latter step can be facilitated by first drawing two more horizontal lines through the station of interest, one at the height of the station""s intersection with the sheer line and the other at the height of the station""s intersection with the bottom line, marking on those two horizontal lines the respective offsets of the sheer line and bottom line for that station.) Alternately, one can transfer the Reference Point to the proper position with respect to the midships stations and draws in the new frame within the conventional body design emanating from that station.
15. You now is in a position to do the half-frames for stations in between the ones defined at the outset. For example, one could do the half frame for the station halfway between the sternmost station and the next station forward, interpolating to get the correct offsets needed to orient the SFC template at each station after pinning it down using the Reference Line and Reference Mark. In this way, create all of the frames that the vessel needs for a sufficient specification of its shape and subsequent construction. This number may be as few as ten or as many as one hundred or more, depending on the type of vessel being created.
16. At this point, the lines drawing is completed, and can be used to make a three-dimensional scale model as well as to produce a full-size drawing on the floor of the shop where the vessel is to be constructed. For the latter, you first scale up the SFC template so as to produce full-size SFC template. A mold is also made from the full-size SFC template, a mold that will used in the traditional manner to make all of the frames for the vessel.